Devices and methods for endovascular electrography

ABSTRACT

An adapter for an endovascular device and a catheter steering device are provided. The adapter for an endovascular device includes a body, a conductive metal ring and a conductive wire. The body includes a first open end, a second open end, a central lumen having a substantially cylindrical surface extending from the first open end to the second open end, and a channel extending from the central lumen to an external opening. The conductive metal ring is attached to the surface of the central lumen, and the conductive wire is coupled to the conductive metal ring and extends through the channel and the external opening. The steering device for a catheter that has a plurality of lumens with spaced distal openings includes a stylet for disposition within one of the plurality of lumens, and a steering member for disposition within a different one of the plurality of lumens. In the installed position, the stylet and the steering member are connected together at respective distal ends such that a portion of the steering member is disposed outside of the distal end of the catheter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-In-Part (CIP) of U.S. patentapplication Ser. No. 12/815,331, filed on Jun. 14, 2010, now U.S. Pat.No. 9,339,206 which claims priority to U.S. Provisional PatentApplication No. 61/213,474, filed on Jun. 12, 2009, the disclosures ofwhich are incorporated herein by reference in their entirety. Thisapplication also claims the benefit of U.S. Provisional PatentApplication No. 61/272,025, filed on Aug. 10, 2009, the disclosure ofwhich is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to endovascular device positioning.Specifically, the present invention relates to an adapter for anendovascular device and a steering device for a catheter.

BACKGROUND OF THE INVENTION

The electrical conduction system of the heart creates specificelectrical signals, electrical energy distributions and behaviorsthereof which are indicative of specific locations in the thoraciccavity and/or of specific heart functions or conditions. When measuredendovascularly, i.e., from within blood vessels or from within theheart, certain parameters of the electrical activity of the heart can beused to identify specific locations in the cardiovascular system and/orfunctional conditions, normal or abnormal. Moreover, by locally andaccurately identifying the location and the type of condition, therapyof such conditions can be optimized and the effect of the therapymonitored in real-time.

Two types of clinical applications are typically addressed. The first isrelated to guiding endovascular devices through the cardiovascularsystem, while the second is related to the non-invasive or the minimallyinvasive remote monitoring of the electrical activity of the heart.

The guidance, positioning, and placement confirmation of endovascularcatheters are necessary in a number of clinical applications, such as,for example:

-   -   1. Central venous access, e.g., CVC, PICC, implantable ports;    -   2. Hemodialysis catheters;    -   3. Placement of pacemaker leads;    -   4. Hemodynamics monitoring catheters, e.g., Swan-Ganz and        central pressure monitoring catheters; and    -   5. Guiding guidewires and catheters into the left heart.

The location of the catheter tip is very important to the patientsafety, the duration and the success of the procedure. Today's goldenstandard for confirming the target location of the catheter tip is thechest X-ray. In addition, there are currently two types of real-timeguiding products available on the market, which try to overcome thelimitations of chest X-ray confirmation: electromagnetic and ECG-based.In hospitals where real-time guidance is used results have improved interms of reducing the number of X-rays, the procedure time, and the costof the procedure. Under real-time guidance first-time success rate hastypically increased from 75%-80% to 90%-95%. In addition, in hospitalswhere ECG guidance is used, e.g., in Italy, Belgium, Germany, chestX-ray confirmation has been eliminated for more than 90% of thepatients. Electromagnetic systems are used mostly in the United Stateswhile ECG-based systems are used mostly in Europe. Amongst other factorswhich determine the difference between the markets in the United Statesand Europe in terms of technology adoption: a) type of health carepersonnel allowed to perform procedures: nurses have more flexibility inthe United States, b) type of devices placed: PICCs are placed more andmore often in the United States, c) price sensitivity: the Europeanmarket seems to be more price sensitive, and d) the current guidingdevices are commercialized by specific manufacturers to work exclusivelywith their catheters: market penetration of the guiding systems reflectsthe market penetration of the catheter manufacturer.

It was also found that different opinions exist regarding where thetarget tip location should be: for example, lower third of the SVC orRA. Therefore guiding technologies should allow for discrimination ofthese locations. The chest X-ray, which is the current golden standarddoes not always allow for such discrimination requiring an accuracy oftypically better than 2 cm. Also, because ECG-based systems make use ofphysiological information related to the heart activity, their abilityto guide placement is accurate with respect to the anatomy. This is notthe case with electromagnetic guiding systems which measure the distancebetween the catheter tip in the vasculature and an external referenceplaced typically on the patient's chest. Because of this aspect,ECG-based systems can be used to document the final result of thecatheter placement potentially replacing the chest X-ray as the goldenstandard.

One of the most valuable diagnostic tools available, the ECG records theheart's electrical activity as waveforms. By interpreting thesewaveforms, one can identify rhythm disturbances, conductionabnormalities, and electrolyte imbalance. An ECG aids in diagnosing andmonitoring such conditions as acute coronary syndromes and pericarditis.The heart's electrical activity produces currents that radiate throughthe surrounding tissue to the skin. When electrodes are attached to theskin, they sense these electrical currents and transmit them theelectrocardiograph. Because the electrical currents from the heartradiate to the skin in many directions, electrodes are placed atdifferent locations on the skin to obtain a total picture of the heart'selectrical activity. The electrodes are then connected to anelectrocardiograph device, or computer, and record information fromdifferent perspectives, which are called leads and planes. A leadprovides a view of the heart's electrical activity between two points orpoles. A plane is a cross section of the heart which provides adifferent view of the heart's electrical activity. Currently, theinterpretation of an ECG waveform is based on identifying waveformcomponent amplitudes, analyzing and then comparing the amplitudes withcertain standards. Modifications of these amplitude components areindicative of certain conditions, e.g., the elevation of the ST segmentor of certain locations in the heart, e.g., the amplitude of the P-wave.In today's practice ECG monitors are widely used to record ECGwaveforms. More and more often applications are made available forautomatic identification of the ECG amplitude components. In certaincases tools are available for decision making support and for automaticinterpretation of ECG amplitude components with respect to underlyingheart conditions.

Remote patient monitoring is a well established medical field. Stillremote monitoring of heart conditions is not as widely accepted as itwould be need and possible. One of the reasons is related to therelatively complicated way of acquiring signals related to the heartactivity, in particular ECG signals. Another important limiting factorof the current remote monitoring technologies is the use ofcommunications channels, like the telephone line, which are difficult tointerface with at both the patient and the physician ends.

SUMMARY OF THE INVENTION

Embodiments of the present invention advantageously provide an adapterfor an endovascular device and a steering device for a catheter.

According to one embodiment of the present invention, an adapter for anendovascular device includes a body, a conductive metal ring and aconductive wire. The body includes a first open end, a second open end,a central lumen having a substantially cylindrical surface extendingfrom the first open end to the second open end, and a channel extendingfrom the central lumen to an external opening. The conductive metal ringis attached to the surface of the central lumen, and the conductive wireis coupled to the conductive metal ring and extends through the channeland the external opening.

According to another embodiment of the present invention, a steeringdevice for a catheter that has a plurality of lumens with spaced distalopenings includes a stylet for disposition within one of the pluralityof lumens, and a steering member for disposition within a different oneof the plurality of lumens. In the installed position, the stylet andthe steering member are connected together at respective distal endssuch that a portion of the steering member is disposed outside of thedistal end of the catheter.

There has thus been outlined, rather broadly, certain embodiments of theinvention in order that the detailed description thereof herein may bebetter understood, and in order that the present contribution to the artmay be better appreciated. There are, of course, additional embodimentsof the invention that will be described below and which will form thesubject matter of the claims appended hereto.

In this respect, before explaining at least one embodiment of theinvention in detail, it is to be understood that the invention is notlimited in its application to the details of construction and to thearrangements of the components set forth in the following description orillustrated in the drawings. The invention is capable of embodiments inaddition to those described and of being practiced and carried out invarious ways. Also, it is to be understood that the phraseology andterminology employed herein, as well as the abstract, are for thepurpose of description and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conceptionupon which this disclosure is based may readily be utilized as a basisfor the designing of other structures, methods and systems for carryingout the several purposes of the present invention. It is important,therefore, that the claims be regarded as including such equivalentconstructions insofar as they do not depart from the spirit and scope ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram that depicts an apparatus according to anembodiment of the present invention.

FIG. 1B is a block diagram of an electronic module for acquisition andprocessing of endovascular electrocardiogram according to an embodimentof the present invention.

FIG. 2 depicts an adaptor for an endovascular device according to anembodiment of the present invention.

FIG. 3 depicts a catheter steering device according to an embodiment ofthe present invention.

FIGS. 4A, 4B, 4C, and 4D depict electrode configurations that provideoptimal acquisition of endovascular electrocardiogram according tovarious embodiments of the present invention. FIG. 4A depicts a singlelead configuration, FIG. 4B depicts a modified 3-lead configuration withmonitoring and guiding capabilities, FIG. 4C depicts a telemetryconfiguration with a single grounded lead, and FIG. 4D depicts one useof ECG monitors for guiding endovascular devices.

FIG. 5 illustrates exemplary electrocardiogram signal amplitudes atdifferent locations in the central venous system.

FIG. 6 illustrates exemplary electrocardiogram signal power spectra atdifferent locations in the central venous system.

FIG. 7 illustrates exemplary electrocardiogram signal electrical energydistribution at different locations in the central venous system.

FIG. 8 depicts a graphical user interface according to an embodiment ofthe present invention.

FIG. 9 depicts a graphical user interface according to anotherembodiment of the present invention.

FIGS. 10A and 10B depict a exemplary printouts for the informationdisplayed by the graphical user interface, according to an embodiment ofthe present invention.

FIG. 11 is a block diagram for a computer-based method for positioningan endovascular device in or near the heart using electrocardiogramsignals.

FIG. 12 illustrates another decision support algorithm for acomputer-based method for positioning an endovascular device in or nearthe heart using electrocardiogram signals, according to an alternativeembodiment.

FIG. 13 illustrates the cardiac conduction system of the heart.

FIG. 14 illustrates electrical signal propagation in the conductionsystem of the heart.

FIG. 15 illustrates electrical activity in the cardiovascular system dueto neuronal control system.

FIG. 16 illustrates a framework for analyzing the endovascularelectrography signals, according to an embodiment of the presentinvention.

FIG. 17 illustrates several embodiments for electrogram waveformprocessing.

DETAILED DESCRIPTION

The invention will now be described with reference to the drawingfigures, in which like reference numerals refer to like partsthroughout.

Embodiments of the present invention advantageously provide an inventiveapparatus(es), computer-based data processing algorithms and methods forobtaining and using endovascular ECGs in a number of clinicalapplications and settings. For example, once device can be used to guideendovascular devices in and around the heart, e.g., guiding centralvenous access devices in the superior vena cava, right atrium, and rightventricle. Such central venous access devices may include central venouscatheters (CVC), peripherally inserted central catheters (PICC),implantable ports, hemodialysis catheters, tunneled catheters andothers. Other devices which may benefit from guidance with the inventiveapparatus are temporary pacemaker leads placed through the centralvenous system. Catheters and guidewires used in left heart proceduresmay also benefit from the present invention by decreasing the amount ofcontrast and radiation required to guide these devices in position. Inanother example, the apparatus can be used for minimally invasivemonitoring and assessing heart conditions based on its electricalactivity, e.g., assessing preload in a heart cycle or monitoring STsegments and T-waves in congestive heart failure.

In one aspect of the invention, an apparatus is described consisting ofsterile adaptors, an electronic module for signal acquisition, acomputer module, software, and peripheral devices and connections. Inone embodiment, the electronic module for signal acquisition can bededicated to acquiring and processing endovascular electrical signalsgenerated by the body (endovascular ECG), in another embodiment theelectronic module can be dedicated to acquiring and processingendovascular ECGs as well as skin ECGs.

In one embodiment, the electronic module and the computer module can beseparate modules, in another embodiment they can be integrated in thesame module and enclosure, and yet in another embodiment they cancommunicate with each other via a wireless connection, such asBluetooth. In one embodiment, the apparatus can contain an integratedprinter, while in another embodiment the printer can be external andattached to the apparatus and the apparatus connected via network, e.g.,wireless to other devices. In yet another embodiment the apparatus canbe used for telemetry and for transmitting the endovascular electrogramsto a remote location, e.g., via a telephone line, Internet, and/orwireless phone. Any combination of embodiments mentioned above is alsopossible.

In another aspect of the invention, various configurations allow theconnection of endovascular devices, such as central venous accessdevices, to the electronic module for signal acquisition and processing.In one embodiment, the device consists of a connecting wire with twoends and special connectors at each end. At one end, the wire can beconnected to a metal or nitinol guidewire or stylet as commonlyavailable on the market. At the other end, the wire can be safelyconnected to the electronic module. In another embodiment, the deviceincludes a coated guidewire, e.g., made of nitinol or stainless steelwith uncoated distal and proximal ends and cm markings. In such anembodiment, the coated guidewire is inserted endovascularly, while theconnecting wire is connected to the proximal end of the coatedguidewire. In another embodiment, the device includes a catheter-syringeadaptor provided with an electrical connecting wire. At one end, theelectrical connecting wire is in contact with the fluid, e.g., salineflowing within the catheter-syringe adapter. At the other end theconnecting wire can be connected to the electronic module.

In another aspect of the invention, various electrode configurationsallow for the optimal acquisition of endovascular ECGs. In oneembodiment, a single lead is used to provide information about the tiplocation of an endovascular device within the vasculature. In anotherembodiment a modified three lead configuration is used to providesimultaneous 3-lead monitoring of the heart activity at the same timewith providing tip location information. In another embodiment amodified single lead configuration plus ground is used for telemetry andtransferring information from the tip of the catheter remotely.

In another aspect of the invention algorithms are introduced for theanalysis of the ECG waveforms and for supporting decision making basedon these waveforms. These algorithms discriminate between differentlocations in the vasculature and assess body functions (systemic and atspecific locations in the body), in particular heart functionality. Invarious embodiments, these algorithms use time domain analysis ofwaveforms: morphologic, for example shape; statistic, for examplebehavior.

In other embodiments, the algorithms use frequency domain analysis ofwaveforms: morphologic, for example shape; statistic, for examplebehavior. In further embodiments, signal energy analysis in time andfrequency domains is also performed, morphologic and statistic. Fuzzy,statistical, and knowledge-based decision making are also contemplatedby the present invention as decision support tools.

In another aspect of the invention, a user interface is provided thatadvantageously simplifies interpretation of data and workflow. In oneembodiment the user interface includes simplified graphics showing thelocation in the vasculature and in the heart of the tip of theendovascular device in use without showing any of the ECG waveforms. Inanother embodiment, the user interface shows, in real-time, the changein location of the tip of the endovascular device in use.

In another aspect of the invention, several inventive methods arepresented which use the apparatus described herein in clinicalapplications. In one embodiment, a computer-based method is providedthat guides central venous catheters (CVC, PICCs, hemodialysis,implantable ports, and others) using stylets, guidewires and salinesolution to the superior vena cava, inferior vena cava, the rightatrium, and the right ventricle. This method is advantageously lesssensitive to patients with arrhythmias than the prior art, andrepresents an alternative to chest X-ray confirmation of tip location ofcentral venous catheters in most clinical cases. In another embodiment,a computer-based method is provided that guides coated guidewires in theright and left heart. In another embodiment, a computer-based method isprovided that guides the placement of temporary pacemaker leads throughthe central venous system. In another embodiment, a method is providedthat is minimally invasive and monitors preload using depolarization andheart rhythms. In another embodiment, a method is provided that isminimally invasive and monitors arrhythmias using P-wave analysis. Inanother embodiment, a method is provided that is minimally invasive andmonitors heart failure using ST segment and T-wave analysis.

FIG. 1A is a block diagram that depicts an apparatus according to anembodiment of the present invention.

The apparatus 100 can be attached through an adaptor (120) to a largevariety of commercially available and custom designed vascular accessdevices (110). Examples of such devices are: central venous catheters(CVC), peripherally inserted central catheters (PICC), implantableports, tunneled catheters, hemodialysis catheters, guiding catheters forpacemaker leads, guidewires used for coronary and other vascularinterventions, guiding catheters for coronary and other vascularinterventions, stylets, syringe needles, and others. If the vascularaccess devices is a stylet, a guidewire, or a syringe needle, itsmaterial must be sufficiently electrically conductive, e.g., stainlesssteel or nitinol. In such a case the hook or the alligator clip adaptoraccording to the present invention should be used If the vascular accessdevices is a catheter, than saline should be used to establish aconductive path through one of the catheter's lumens. In such a case,the syringe-catheter adaptor according to the present invention shouldbe used.

The electronic module (130) receives electrical signals from the adaptorand from one or more other electrodes placed on the patient's skin(115). Alternatively, more than one adaptor can be used at the same timeto connect to more than one endovascular device in order to providedifferent electrical signals to the electronic module. The use of skinelectrodes is optional in certain device configurations. The electronicmodule processes the electrical signals and transmits them to a computermodule (140) for further processing and other functions. In oneembodiment the electronic module and the computer module can be packagedseparately, and in another embodiment they can be integrated in the samepackage. In one embodiment, the connection between the electronic moduleand the computer module can be hardwired (131), and in anotherembodiment the connection can be wireless(132), e.g., using Bluetooth.

The computer module processes the signals from the electronic moduleapplying algorithms (170) as described by the current invention. Thecomputer module can also be connected to peripherals (160), e.g., aprinter or a label printer and storage devices and provides connectivityincluding wireless connectivity (150) to other computers or to theinternet. The storage device can be used to store a database ofknowledge and information regarding the application at hand. Theconnectivity interface can be used to update this database remotely withnewest relevant knowledge and information, e.g., new clinical cases, newfindings regarding the relationship between electrograms and heartconditions. The computer module supports a graphical user interface(180) optimized for the purpose of the clinical application at hand.

FIG. 1B is a block diagram of an electronic module (2) for acquisitionand processing of endovascular electrocardiogram according to anembodiment of the present invention.

The patient connector interface (10) allows for connecting electricalleads to the patient (5). Any combination of skin electrodes and/orelectrical connections to endovascular devices using the adaptorsdiscussed above can be used. In one embodiment, the amplifier (20) is afour stage amplifier with variable gain, which can amplify electricalsignals coming through the patient cable, for example, typical ofelectrocardiographic values. The analog-to-digital converter (30)converts the signals in digital format readable by the micro-processor(40). Any number and configurations of microprocessors,microcontrollers, and digital signal processors can be used to implementthe micro-processing function (45).

In one embodiment, a microcontroller is responsible for controlling theserial communication with a computer module (90) via the serialinterface (70) or via the wireless interface (80) and a digital signalprocessor (DSP) is responsible for implementing one or several of theinventive algorithms described herein. Alternatively, a single processor(46) can be used for both communication and processing.

The micro-processor (40) also receives commands from the computer module(90) and controls different elements of the electronic module, e.g., theamplifier (20) accordingly. The patient isolation block (50) decoupleselectrically the power (60) and the serial communication channel (70)from the patient interface (10) in order to ensure patient protection toelectrical shock. In one embodiment the isolation block (50) canconsists of a transformer and/or couplers, e.g. optical couplers.

FIG. 2 depicts an adaptor (200) for an endovascular device according toan embodiment of the present invention. Vascular access devices likecatheters, syringes, syringe needles, stopcocks, infusion pumps andothers connect to each other through standard connections. For example,in FIG. 2 such a standard connection between two devices is illustratedon device (201) by the luer (202) with inner diameter (203) and outerdiameter (204), and on device (250) by threaded port (251) with innerdiameter (252) and fluid opening diameter (253). The threaded port (251)and the luer (202) allow for connecting the two devices (201, 250) bythreading, attaching, coupling, etc., the port (251) into the luer(202).

The adaptor (200) has a body (220) with two ends (226, 227) with alength (225), and is made, for example, of strong biocompatible plasticmaterial with some degree of elasticity. End (227) has a shape of acone. In one embodiment, end (227) has an elastic sealing portion (228)such that end (227) can easily fit in the luer (202) of device (201) toseal the connection for fluid flow. The other end (226) is in the shapeof a standard luer, such as, for example, luer (202) of device (201).The threaded port (251) of the device (250) can be connected to end(226) of the adaptor (200). The cone piece (227) also allows aconnection to a device that does not have a luer. The stand alone conepiece (270) allows a connection between two devices with differentaccessible diameters. The end (227) of adaptor (200) has a diameter(223) and fits inside the diameter (272) of the cone piece (270). Theend (271) of the cone piece (270) fits in a simple catheter end portion(261) with a diameter (262) of a typical device (260). For example,device (260) can be a catheter for an implantable port.

In one embodiment, device (201) is a syringe needle, and device (250) isa syringe. Fluid, e.g., a conductive electrolyte, flows through adaptor(200) through a central inner bore or lumen (222) having a certaindiameter, and provides a fluid path between the devices (250, 201). Aconductive metal ring (240) is attached to a portion of thesubstantially cylindrical surface of lumen (222) and, preferably,induces very little perturbations to the fluid flow. For example, themetal ring (240) may be disposed within a recessed portion of thesubstantially cylindrical surface of the lumen (222). One end (230) of aconductive wire (233) is electrically coupled to the metal ring (240);in one embodiment, the end (230) is soldered to metal ring (240). Inanother embodiment, the end (230) is captured between the surface of thelumen (222) and the metal ring (240), and the end (230) and the metalring (240) maintain good electrical contact through mechanical pressure.The wire (233) may be bare or insulated. In a preferred embodiment, themetal ring (240) is fixedly attached to the surface of lumen (222)using, for example, adhesive, an interference fit, a press fit, etc.,while in other embodiments, the metal ring (240) may be removablyattached to the surface of lumen (222), free-floating, etc.

The wire (233) passes through a channel (231), which extends from thelumen (222) to an opening in the outer surface of the body (220). Epoxy(232), or other suitable material, may be used to seal the opening ofthe channel (231), as well as to provide a strain relief for the wire(233). The metal ring (240) may be advantageously disposed adjacent tothe channel (231) to provide additional sealing. Thus, the metal ring(240), the wire (233), the channel (231) and the epoxy (232) provide asealed, electrical connection to the fluid flowing through the adaptor(200). A connector (234) may provide a standard electrical connection tothe electrography system; a non-terminated wire may also be used. In oneembodiment, the wire (233) terminates at the opening of the channel(231) and the connector (234) is attached directly to the body (222),while in another embodiment, the wire (233) extends through the openingof the channel (231) and the connecter (234) is attached to the free endof the wire (233).

In one embodiment, the substantially cylindrical surface of lumen (222)is tapered along the longitudinal direction (221). This taper may extendalong the entire length of lumen (222), or restricted to a certainportion thereof. For example, the surface of lumen (222) may becone-shaped and have a larger diameter at the proximal end, or,alternatively, the larger diameter may be located at the distal end.

In one example, device (201) is a syringe needle that is inserted into alumen of a catheter for an implantable port, and device (250) is asyringe. The syringe is filled with saline, which is then injected intothe catheter through the adaptor (200). Thus, the adaptor (200) becomesfilled with saline solution, and, because the conductive metal ring(240) is in contact with saline and the conductive wire (233), anelectrical connection is established between the catheter lumen and thewire (233). In this way, the electrical signal at the tip of thecatheter may be measured through the saline solution. Other electricallyconductive solutions may also be used to obtain the endovascularelectrogram using the adaptor (200). In another embodiment, the adaptor(200) may be used with infusion pumps, as well as other types of powerinjections. In an alternative embodiment, the adaptor (200) does notinclude the metal ring (240), and the electrically conductive ending(230) is in direct contact with the electrolyte.

FIG. 3 illustrates a catheter steering device according to an embodimentof the present invention. In this embodiment, the catheter (300) is atriple lumen catheter and the distal end of each of the lumens is spacedwith respect to each other. The catheter steering device can be usedwith any catheter having two or more lumens with spaced distal lumenopenings. The open end of one lumen (306) of catheter (300) is at thevery distal end of the catheter, another end or opening of a lumen (305)is spaced back from the distal end and the end or opening of the thirdlumen (307) is spaced back compared to the second end (305). Thedistance between the open end (306) and the end (307) is typically fromone to several centimeters.

Several types of catheters have multiple lumens with spaced ends, andthe inventive steering device can accommodate such catheters. Forexample, in the case of a peripherally inserted central catheter, thetypical length of a catheter is 50 to 60 centimeters and the spacingbetween the distal lumen ends (305, 306, and 307) is from one to severalcentimeters. A hemodialysis catheter with two lumens can typically be 20to 40 centimeters in length, with one to several centimeters spacingbetween the distal ends of the two lumens. A multi-lumen central venouscatheter (CVC) can typically be 15 to 25 cm in length with spacingbetween distal ends or openings of the lumens being from severalmillimeters to several centimeters.

At the proximal end, the catheter has a catheter hub (301) which splitsthe three lumens and connects each of them with a luer (302, 303, 304).The inventive catheter steering device includes a stylet (310) with ahandle (311) at the proximal end to allow for pushing, pulling, andremoval after use, and a steering member (320) which connects to thedistal end of the stylet (322) and which can be fed back into a distallumen opening of one of the other lumens, such as, for example, lumen(307). The steering member (320) returns to the proximal end of thecatheter through the catheter lumen and exits at the proximal endthrough the luer corresponding the respective lumen (304). So disposed,the steering device is in the installed position. In one embodiment, themember (320) has a handle (321) which can be used to pull the memberthrough the lumen. In another embodiment, the handle (321) is detachablefrom the member (320).

The member (320) may be polyurethane, silicone, PTFE, or other similarmaterials. In different embodiments, the member (320) may be any kind ofbiocompatible thread, e.g., surgical thread. In another embodiment, themember (320) is stainless steel wire. In one embodiment, the stylet isprovided pre-inserted into one of the catheter lumens, typically thecentral lumen with the most distal opening (306) with the member 320attached at the distal end of the stylet (322) and pre-inserted into thelumen (304) through the lumen opening (307). In order to steer thecatheter, the user pulls the member 320 out of the catheter whilepreventing the stylet 310 to be pulled into the catheter. Thus, thecatheter tip can be bent in a desired direction. This situation isillustrated by the bent catheter tip (350), the member (340) which waspulled back and the member (330) which is its initial position withrespect to the catheter. If the stylet (310) or the steering member(320), or both are made of any electrically conductive material, theneach or both of them can be used to measure electrical signals orendovascular electrograms at the distal tip of the catheter byconnecting their proximal ends to the endovascular electrography system.In one embodiment, the steering member (320) can be tied to the stylet(310) through the opening (307) of the catheter lumen.

In another embodiment, the stylet (310) and the steering member (320)are manufactured as a single component to form an extended steeringmember that is looped back through the opening (305) of a differentcatheter lumen. By pulling one of the two ends of the extended steeringmember coming out through luers (304) and (302), the same effect isachieved and the catheter tip can be bent in a desired direction. Inanother embodiment, in the case of a double lumen catheter, the stylet(310) can be inserted in one lumen and the steering member (320) can beinserted in the other lumen, such that the effect of bending thecatheter tip can be achieved by pulling the proximal ends. In a furtherembodiment, the steering member (320) can be inserted in the lumen (302)and through the opening (305).

FIGS. 4A, 4B, 4C, and 4D depict electrode configurations that provideoptimal acquisition of endovascular electrocardiogram according tovarious embodiments of the present invention.

FIG. 4A depicts a single lead configuration with a reference electrode(410), for example attached to the patient's skin over the right arm andwith the other electrode attached through an adaptor to an endovasculardevice (415). The reference electrode attached to the skin over theright arm is presented in this configuration for illustration purposesonly. Other locations of the reference electrode are possible dependingon the type of ECG required. The reference electrode over the right armtogether with the tip of the endovascular device used with the adaptorcan be similar to lead II of a standard ECG. In this case the ECGsobtained from the superior vena cava (401) and inferior vena cava (402)can be optimized. The reference electrode can be attached to the skin inany other location in order to simulate other leads of the standard ECG.The reference electrode can be also connected to adaptors attached toother endovascular devices in order to obtain more local informationfrom within the patient's heart (400).

FIG. 4B depicts a modified 3-lead configuration, with monitoring andguiding capabilities, with 4 electrodes. Three (3) electrodes correspondto the standard ECG electrodes: right arm (RA, 420), left arm (LA, 425),and left leg (LL, 430) used as reference. The fourth electrode isattached through an adapter to the endovascular device (C, 435). In thisconfiguration, the electronic module and the algorithm perform twofunctions simultaneously: the three standard electrodes (RA, LL, and LL)perform a monitoring function of the heart, while the C electrode (435)allow for recording the ECG at the tip of device.

FIG. 4C depicts a telemetry configuration with a single grounded lead,including the configuration illustrated in FIG. 4A and a groundreference (450). This configuration can be used to transmit ECGsremotely through a telemetry system configuration.

FIG. 4D depicts one use of ECG monitors for guiding endovasculardevices. A standard ECG monitor is used having standard inputs RA (465),LA (460), and LL (470). LA (460) is connected to the left arm and LL(470) to the left leg of the patient. The RA input (465) is connected toa switch which can be used be the clinician to switch the RA input (465)between the RA electrode and the catheter (C) electrode 475. Thus eithermonitoring or guiding of catheter placement can be achievedalternatively.

FIG. 5 illustrates exemplary electrocardiogram signal amplitudes atdifferent locations in the central venous system.

The heart (504), right atrium (501), superior vena cava (SVC) (502), andthe inferior vena cava (IVC) (503) are illustrated. Location A is in theupper SVC, location B is in the lower third of the SVC, location C is atthe caval-atrial junction, location D is in the right atrium, andlocation E is in the upper inferior vena cava.

Graph 510 illustrates an ECG waveform as a function of time at recordedat location A. The absolute amplitude of the waveforms is recorded on anamplitude scale (590). In the case of an endovascular ECG, the standardelements of the electrocardiogram are illustrated: the P-wave (560), theR-wave (570), and the T-wave (580). The amplitudes and shape at locationA recorded with a lead configuration as in FIG. 4D are similar to anelectrocardiogram recoded at the skin level with the same electrodeconfiguration.

Graph 520 illustrates an endovascular ECG depicted at location B. Theamplitude at this location is higher than the one at location A but theoverall shapes of the waveform are similar at location A and B.

Graph 530 illustrates an endovascular ECG depicted at location C. Atlocation C at the caval-atrial junction, the amplitude of the waveformis yet higher than the one at location B and the P-wave has dramaticallychanged becoming higher than the R-wave. This waveform is an indicationof the proximity of the sino-atrial node.

Graph 540 illustrates an endovascular ECG depicted at location D. Atlocation D in the right atrium, the amplitudes are similar to location Cbut the P-wave changes polarity becoming bi-polar. This is an indicationthat the measurement of the ECG occurs beyond the sino-atrial node.

Graph 550 illustrates an endovascular ECG depicted at location E. Atlocation E in the inferior vena cava, the waveform is similar to the oneat location A in terms of amplitude except the P-wave has reversepolarity. The differences in the ECG waveforms at different locationsare used by the algorithms introduced herein to discriminate between thecorresponding locations and to assess heart and blood vesselfunctionality.

FIG. 6 illustrates exemplary electrocardiogram signal power spectra atdifferent locations in the central venous system, using a spectral scale(690).

The heart (604), right atrium (601), superior vena cava (SVC) (602), andthe inferior vena cava (IVC) (603) are illustrated. Graph 610illustrates an endovascular ECG spectrum depicted at location A. Atlocation A, the spectrum (610) has the appearance of a single centralfrequency or single band (660) and with a frequency distributionspectral power and energy similar to those at skin level.

Graph 620 illustrates an endovascular ECG spectrum depicted at locationB. At location B the frequency distribution has two major bands and ahigher energy and spectral power than the one at location A.

Graph 630 illustrates an endovascular ECG spectrum at location C. Atlocation C, there are multiple (3-4) major frequencies or principalspectral components distributed over a wider range of frequencies (670).This spectral distribution is indicative of the energy distributionaround the sino-atrial node. The spectral power and signal energy haveincreased compared to location B.

Graph 640 illustrates an endovascular ECG spectrum depicted at locationD. At location D the spectrum is wider and more broadband indicative ofthe electrical activity of the right atrium.

Graph 650 illustrates an endovascular ECG spectrum depicted at locationE. The frequency spectrum at location E is similar to the one atlocation A. The differences in the spectral waveforms at differentlocations are used by the algorithms introduced herein to discriminatebetween the corresponding locations and to assess heart and blood vesselfunctionality.

FIG. 7 illustrates exemplary electrocardiogram signal electrical energydistribution at different locations in the central venous system. Theheart (704), right atrium (701), superior vena cava (SVC) (702), and theinferior vena cava (IVC) (703) are illustrated. Graphs (710, 720, 730,740, 750) depict the energy distribution at different locations (A, B,C, D and E, respectively) and the changes in time are used by thealgorithms introduced herein to discriminate between the correspondinglocations and to assess heart and blood vessel functionality.

Considering FIG. 16 for a moment, a framework for analyzing theendovascular electrography signals according to an embodiment of thepresent invention is illustrated. The heart is represented by (1600),the superior vena cava by (1601), the inferior vena cava by (1602) andthe right atrium by (1603). In this embodiment, there are three regionsof interest for placing central venous access devices: the lower thirdof the superior vena cava or SVC (1605), the caval-atrial junction orCAJ (1606), and the upper right atrium or RA (1607).

The graph (1620) illustrates the electrical energy profile as a functionof location in the heart and the graph (1640) illustrates the differentelectrography waveforms which can be obtained at different locations inthe heart. The curve (1630) illustrates the increase of electricalenergy detected in each of the regions at the tip of an endovascularcatheter advancing from the superior vena cava into the heart. In oneembodiment, the energy curve is calculated in time domain, while inanother embodiment, the energy curve is calculated in the frequencydomain using the frequency spectrum. In one embodiment, the energy iscalculated for the actual signal levels, while in another embodiment,the baseline value or other mean values are first subtracted from thesignal values before energy calculations. The signal energy or power iscalculated in time domain by summing up the squared amplitude valuesbefore and/or after baseline subtraction over a determined period oftime, e.g., a heart beat. In the frequency domain, the signal energy orpower is calculated by summing up the squared values of the frequencycomponents. In one embodiment, the curve is calculated using the entireelectrogram, while in other embodiments, only certain segments of theelectrogram are used for the energy calculations, e.g., only the segmentcorresponding to a “P-wave” of an electrocardiogram. Such a “P-wave”segment is representative of the electrical activity of the sino-atrialnode.

Different levels of energy characterize the different locations alongthe catheter path from the SVC to the heart. These regions can bedifferentiated in terms of their electrical energy level by usingthresholds. Threshold (1631) of energy level defines the beginning ofthe lower third of the superior vena cava. The energy levels (1621)define the regions in the vasculature of low energy which are distant orfurther away from the sino-atrial node. The energy levels (1622) betweenthresholds (1631) and (1632) define the region labeled as the lowerthird of the superior vena cava (1625 and 1605). The energy levels(1623) between thresholds (1632) and (1633) define the region labeled asthe caval-atrial junction (1626 and 1606). The energy levels (1624)between thresholds (1633) and (1634) define the region labeled rightatrium (1627 and 1607).

Similarly, the shape and size of the electrogram in graph (1640)relative to a baseline (1650) can be correlated to a location in theheart. Thresholds (1631), (1632), (1633), and (1634) are determinedspecifically for the type of energy considered for calculations, e.g.the entire electrogram, the P-wave, and/or the S-T segment. Before thelower third of the SVC and corresponding to a relatively low level ofenergy (1621), the P-wave (1651) and the R-wave (1652) are similar insize and shape with a standard electrocardiogram lead II recorded at theskin level if the right arm standard ECG lead is connected to thecatheter and measuring the electrogram signal at the tip of thecatheter. In the lower third of the SVC (1605 and 1645), the energylevel of the electrogram increases, the electrogram amplitudes increaseand the P-wave (1653) increases amplitude and energy relative to theR-wave (1654) to where the P-wave amplitude and energy between half andthree quarters of the amplitude and energy of the R-wave. At thecaval-atrial junction (1606 and 1646), the energy level of theelectrogram increases further, the electrogram amplitudes continue toincrease and the P-wave (1655) increases amplitude and energy relativeto the R-wave (1656) to where the P-wave amplitude and energy are largeror equal to the amplitude and energy of the R-wave. In the right atrium(1607 and 1647), the energy level of the electrogram increases further,the electrogram amplitudes increase, the P-wave (1657) becomes bipolarand its amplitude and energy relative to the R-wave (1658) startdecreasing. These behaviors are quantified, analyzed, and used in orderto provide location information regarding the tip of the catheter.

Considering FIG. 17 for a moment, several electrogram waveformprocessing embodiments are illustrated. Graphs (1710) and (1720)illustrate a P-wave analysis embodiment. Since the P-wave corresponds toelectrical activity of the heart generated by the sino-atrial node, thechanges of the P-wave are most relevant with respect to determining theproximity of the sino-atrial node in an endovascular approach.Therefore, in order to assess proximity of the sino-atrial node andlocation in the vasculature, signal analysis methods in time andfrequency domains, as well as signal energy criteria can be applied onlyto the P-wave segment of an electrogram. In graph (1710), the segmentdesignated for the P-wave analysis (1711) starts at moment (1713) andends at moment (1714). During the period of time between the startingmoment and the ending moment of the P-wave segment, the highestamplitude detected corresponds to the P-wave peak (1712). The startingmoment (1713) of the P-wave segment analysis can be determined in anumber of ways. In one embodiment, the heart beat is calculated and theR-peak is detected as the maximum amplitude of the heart beat. Goingback from each R-peak a certain percentage of the heart beat, forexample between 20% and 30%, determines the moment when the analysis ofthe P-wave starts (1713). Going back 2% to 5% of the heart beat fromeach R-peak determines the end of the segment designated for the P-waveanalysis (1714). Similarly, in graph (1720), the designated segment forthe P-wave analysis (1721) starts at moment (1723) in the heart cycleand ends at moment (1724). The P-wave in this case is bipolar with apositive maximum amplitude (1722) and a negative maximum amplitude(1725) when compared to the baseline (amplitude equals zero). For theP-waveform defined between the starting point (1713 on graph 1710 and1723 on graph 1720) and the end point (1714 on graph 1710 and 1724 ongraph 1720) time-domain and frequency-domain algorithms are appliedaccording to the present invention.

Graph (1730) illustrates the advantages of baseline subtraction prior tosignal energy computation. If the signal energy is calculated in timedomain as the sum of the squared signal amplitudes over a heart beat,then the amplitude variations between levels (1731 and 1732) aroundbaseline (1733) may lead to a lower energy level than the signal withamplitude variations between levels (1734 and 1735) whereby the level(1734) is the baseline. The baseline value (1733) is subtracted from theamplitude values (1731 to 1732) and the baseline value (1734) issubtracted from the amplitude values (1734 to 1735). After subtractingthe baseline, the sum of squared amplitude values is calculated. Thus,this sum is proportional to the energy of signal variation around thebaseline and therefore it is more appropriate to characterize changes inthe signal values/behavior.

Graph (1740) shows a typical electrogram waveform with a P-wave (1741)and an R-wave (1742) and a distorted signal with the P-wave covered byhigh frequency noise (1744) and the R-wave saturated to a maximum value(1743). In the presence of these kind of artifacts (1744 and 1743) it isvery difficult and sometimes impossible to recover the original signal(1741 and 1742). Therefore, according to the present invention, analgorithm is used to detect the presence of artifacts and reduce theamount of artifacts as much as possible. If, after reducing theartifacts, the signal cannot be recovered, then the signal is discardedfor the computation of signal energy. The presence of artifacts can bedetected in time domain by a high value of the derivative and of itsintegral, a jump in signal energy, a jump in the value of the baselineor in different averages calculated form the signal. In frequencydomain, the artifacts can be detected as a jump in the value of the DCcomponent (frequency zero of the spectrum), as the sudden appearance ofhigh frequency components, and in a jump of the spectral power/energy.In the frequency domain, selective filtering can be applied and allcomponents removed, which are not “typical” for the average behavior ofthe signal. After selective filtering, the signal is reconstructed inthe time domain using an inverse Fourier transform in order to allow forverification of the success of the selective filtering.

FIG. 8 depicts a graphical user interface according to an embodiment ofthe present invention.

Window (810) presents the ECG waveform in real-time as it is acquired bythe electronic module using the attached electrode configuration. Window(820) is a reference window and shows a frozen waveform used to comparewith the current window. In one embodiment, the reference waveform inwindow (820) can be obtained through the electrodes connected to theelectronic module at a reference location of the catheter and/or using areference configuration of the skin electrodes. For example, such areference waveform can be the ECG recorded using an adaptor according tothe present invention connected to an endovascular device placed at thecaval-atrial junction. In a different embodiment, the reference waveformin window 820 can be a typical waveform at a certain location in thevasculature or of a certain heart condition as it is recorded in adatabase of waveforms and as it is stored in the storage medium of thecomputer system. If the electrode configuration allows for simultaneousheart monitoring and recording of electrograms using an endovasculardevice, window (830) shows one of the standard ECG leads for heartmonitoring, while window (810) shows the ECG at the tip of theendovascular devices when connected to an adaptor, such as the onesdiscussed above.

The icon (870) is a representation of the heart, and the locations Athrough E (875) illustrate different locations in the heart and vascularsystem which can be discriminated by analyzing endovascular ECGs inaccordance with the methods disclosed herein. As a location in thevasculature is identified by the algorithms, the corresponding place andletter on the icon (875) becomes highlighted or in some other way ismade visible to the user. The bars (884), (885), and (886) show signalenergy levels. The “E” bar (885) presents the amount of electricalenergy computed from the ECG frequency spectrum at the current locationof the tip of the endovascular device. The “R” bar (884) presents theamount of electrical energy computed from the ECG frequency spectrum ata reference location. The “M” bar (886) presents amount of electricalenergy computed from the ECG frequency spectrum using the monitoring ECGsignal from the skin electrodes. The window (840) depicts monitoringinformation, e.g., heart rate. Patient information (name, date ofprocedure and others) are shown in window (850). Window (860) containssystem control elements like buttons and status information, e.g.,scale, scroll speed, system parameters and system diagnostics.

FIG. 9 depicts a graphical user interface according to anotherembodiment of the present invention.

The icon (920) is a representation of the heart and the locations Athrough E (930) illustrate different locations in the heart and vascularsystem which can be discriminated by analyzing endovascular ECGs. As alocation in the vasculature is identified by the algorithms, thecorresponding place and letter on the icon (930) becomes highlighted orin some other way is made visible to the user. The bars (940), (950),and (960) show signal energy levels. The “E” bar (940) depicts theamount of electrical energy computed from the ECG frequency spectrum atthe current location of the tip of the endovascular device. The “R” bar(950) shows the amount of electrical energy computed from the ECGfrequency spectrum at a reference location. The “M” bar (960) showsamount of electrical energy computed from the ECG frequency spectrumusing the monitoring ECG signal coming from the skin electrodes. Thebutton “Print” (960) allows the user to print the informationdocumenting the case on a printer, for example on a label printer forquick attachment to the patient's chart.

FIGS. 10A and 10B depict a exemplary printouts for the informationdisplayed by the graphical user interface, according to an embodiment ofthe present invention.

FIG. 10A illustrates a printout (1000) for the case of a catheter tipplacement procedure in the lower third of the SVC. The field 1010depicts the heart icon whereby the letter “B” corresponding to the lowerthird of the superior vena cava (SVC) is highlighted (1040). Field 1030depicts the reference ECG waveform recorded at the tip of the catheterat the caval-atrial junction in the proximity of the sino-atrial node.Field 1020 depicts the ECG waveform at the tip of the catheter in theposition in which it was placed at the end of the procedure. For FIG.10A, this location is in the lower third of the SVC and the ECG waveformcorresponds to this location. The patient name (1001) and the date ofprocedure (1002) are also printed.

FIG. 10B depicts a similar printout (1050) except that the finalposition at the end of the procedure is at the caval-atrial junction atlocation C (1090) on the heart icon (1060). The “SA Node” field depictsthe reference ECG waveform (1080), and the “Final Position” field (1070)shows that the catheter was placed with the tip at the sino-atrial node:the ECG waveform in final location is similar or even identical with theone in the reference location at the sino-atrial node (SA Node). It isknown that the proximity of the SA Node indicates a location at thecaval-atrial junction. These locations are sometimes consideredidentical by some clinicians.

FIG. 11 is a block diagram for a computer-based method (1100) forpositioning an endovascular device in or near the heart usingelectrocardiogram signals.

The algorithms are applied to the input signal (1102) (ECG) acquired bythe adaptor to the endovascular devices and, optionally, through skinelectrodes as well. The Error Detection Block (1105) detects at leastthree types of error conditions/exceptions, such as, for example, when adefibrillator has been applied to the patient, when a pacemaker isfiring excitation pulses and/or when a lead/electrode is off. Theseerrors/exceptions may be handled differently, and the user may beinformed about the presence of an exception and the way of handling theexception (1110).

The Pre-Processing block (1115) may amplify the signal, reduce noise,eliminate artifacts, etc. In one embodiment, rescaling the signal to thedisplay range occurs under user control and is not automatic, as withmost currently available ECG monitors. Thus, changes in the amplitude ofthe ECGs are easily noticed. A high-pass filter corrects the baselineand reduces such artifacts as respiratory artifact. Wideband noisesuppression may be achieved using a selective filter, e.g., a wavelettransform. Electromagnetic interference with other equipment and thepower grid may be suppressed by a notch filter (narrow band filter)centered at 60 Hz or 50 Hz to accommodate domestic or internationalpower supplies. High frequency noise may be suppressed with a low-passfilter, which, in one embodiment, is implemented with variable lengthaveraging, such as, for example, a running window corresponding to aheart cycle, an averaging of the ECG over several consecutive heartcycles, etc. The Adaptive Filtering block (1120) optimizes the filtercoefficients by minimizing an error signal.

The Time-Domain Pattern Recognition block (1130) identifies elements ofthe ECG waveform, their relationship(s) and their behavior(s) in time.An important aspect of the time-domain pattern recognition algorithm inblock 1130, as well as of the Frequency Domain Patter Recognition block1140, is data history. The ECGs are analyzed in real time for certainelements, and, for other elements, a data buffer with an appropriatebuffer length is maintained in the memory of the electronic and/orcomputer modules in order to allow for historic data analysis andprediction based on this analysis. In one embodiment, the data historybuffer is several seconds long allowing for the ECG signal correspondingto several heartbeats to be saved in the buffer. A double bufferingtechnique allows the waveform in one buffer to be processed while thesecond buffer continues to store signals. Thus no signal data are lostwhile the waveform in one buffer is processed. After data processing onone buffer is completed, the results are sent to the Decision SupportAlgorithms (1150) and the two buffers switch roles. The length of thebuffer accommodates the time duration of data processing in order toensure that no data are lost. A similar double buffering technique isalso applied to the data subject to Frequency Domain Pattern Recognitionblock (1140).

In the case of an endovascular ECG, elements of interest may include,but are not limited to, one or more of the following:

-   -   1. The P, Q, R, S, T, and U waves, their peaks, amplitudes and        duration;    -   2. The duration of the P-R, S-T, and T-P segments/intervals;    -   3. The elevation of the S-T segment;    -   4. The variances of the P-P and R-R intervals;    -   5. The variance of the S-T and of the R-T intervals, etc.;    -   6. The peak-to-peak values of the P-wave and of the QRS complex;    -   7. The ratio of the P-wave and R-wave amplitudes and the ratio        of the P-wave and QRS complex peak-to-peak amplitudes;    -   8. The polarity of the P-wave: single positive, single negative,        or bipolarity;    -   9. The derivative of the P-wave, QRS-complex, and T-wave;    -   10. Temporal average of the R-R interval and the heart beat;    -   11. Maximum value of the P-wave amplitude/peak and of the P-wave        peak-to-peak amplitude over a certain period of time;    -   12. Maximum value of the R-wave amplitude/peak and of the ORS        complex peak-to-peak amplitude over a certain period of time.

Several techniques may be used to derive the information listed abovefrom the ECG waveforms, including, but not limited to, one or more ofthe following:

-   -   1. “Peak detection”;    -   2. Computation of first derivatives;    -   3. Running averages along the signal in one heartbeat and along        multiple heartbeats;    -   4. Adaptive thresholding;    -   5. Auto-correlation.

The Fast Fourier Transform in block (1125) performs a Fast FourierTransform on a number of ECG samples stored in a buffer of a certainlength, e.g., 256, 512, 1024, 2048 or more data samples. The FourierTransform transforms the waveform from the time domain into thefrequency domain.

The Frequency-Domain Pattern Recognition block (1140) illustratesvarious aspects of pattern recognition performed on the ECGs in thefrequency domain, including, but not limited to, one or more of thefollowing:

-   -   1. Principal components analysis, i.e., determination of the        most significant elements of the frequency spectrum (similarly        to determining the morphological elements of the electrograms,        e.g., certain waves and segments in time domain);    -   2. Data compression in order to reduce the amount of computation        based on the principal components;    -   3. Determination of the number and morphology of the principal        components, in particular determination if the spectrum has only        one, two or multiple main frequencies (frequency bands);    -   4. Calculation of the spectral power and of the signal energy        from the frequency spectrum;    -   5. Running average along the frequency dimension over a single        spectrum in order to reduce wideband noise;    -   6. Running average along several spectra in order to filter out        artifacts;    -   7. Determination of additional morphological elements of the        spectrum, e.g., the maximum frequency, the energy contained in        the maximum frequency, the frequency histogram, i.e., what        frequencies contain how much energy, the frequency of the        highest significant maximum energy peak, etc.;    -   8. Calculation of behavior and averages over time of the        principal components and other parameters determined from the        spectral distribution, e.g., determining the maximum value of        the signal energy and of the spectral power over a certain        period of time;    -   9. Determine/estimate certain heart conditions based on the        spectral analysis. This determination/estimation is also        performed in more detailed in the decision support blocks 1150        and 1250.

Several decision support algorithms use the information provided by thetime domain pattern recognition and frequency-domain pattern recognitionalgorithms. In one embodiment, block (1150) supports placing anendovascular device in either the lower third of the SVC or at thecaval-atrial junction.

In particular, block 1150 is based on the concept of first reaching thecaval-atrial junction during catheter placement. At the caval-atrialjunction or near the sino-atrial node the P-wave and other electricalparameters reach a maximum value. At the caval-atrial junction theP-wave is unipolar. After reaching the sino-atrial node at thecaval-atrial junction, i.e., the maximum value of the P-peak amplitudeand spectral power, the catheter is pulled back several centimetersuntil the P-wave decreases to half the amplitude reached at thecaval-atrial junction. At the location where the P-wave has decreased tohalf the amplitude as the caval-atrial junction, the catheter isconsidered to be in the lower third of the superior vena cava. TheP-wave peak amplitude or peak-to-peak amplitude, as well as the spectralpower, is used to map the location in the vasculature to the ECGwaveform.

More particularly, after receiving an endovascular ECG signal associatedwith an endovascular device, the signal is processed, over a pluralityof predetermined time periods, to calculate a P-wave amplitude and aspectral power for each predetermined time period. A maximum P-waveamplitude is then determined from the plurality of P-wave amplitudes, aswell as an associated maximum spectral power from the plurality ofspectral powers. The location at which these maximum values aredetermined is associated with a predetermined location in or near theheart, such as the cava-atrial junction. The location of theendovascular device is then calculated, for each predetermined timeperiod, based on a ratio of the P-wave amplitude to the maximum P-waveamplitude and a ratio of the spectral power to the maximum spectralpower, and the location of the endovascular device is then displayed tothe user. Additionally, the polarity of the P-wave and the R-waveamplitude may also be used to determine the location of the endovasculardevice.

A single criterion or a combination of such criteria can be used tosupport decision making. In one embodiment, T1, T2, and T3 may beempirically established thresholds which are different for each patient,and the algorithm can use an adaptive loop to adjust the thresholdsbased on the current measurements. In another embodiment, thesethresholds are predetermined.

In alternative embodiments, the ratio between the P-peak/P amplitude orthe P-wave peak-to-peak amplitude to the R-peak/R amplitude or to theQRS complex peak-to-peak amplitude can also be used to establishlocation relative to the sino-atrial node. In one embodiment theP-peak/amplitude must be approximately half of the R-peak/amplitude andthe P-wave must be unipolar for the location to correspond to the lowerthird of the SVC. In another embodiment, the P-wave peak-to-peak must behalf of the QRS peak-to-peak amplitude and the P-wave must be unipolarfor the location to correspond to the lower third of the SVC.

As discussed above, the results of the decision support algorithms block1150 may be presented to the user, for example, by high lightening theappropriate location on the heart icon corresponding to the type of ECGidentified by the system (1160).

The decision support algorithm block 1250, depicted in FIG. 12, is basedon comparing the P-wave, R-wave and P-wave spectral power at the currentlocations with the values of these parameters determined from the skinelectrocardiograms in an equivalent lead, e.g., lead II. Thresholds T1through T6 are empirical values subject to adaptive adjustments relativeto each patient. Each of the criteria or a combination of criteria shownin FIG. 12 can be used.

Other decision algorithms can also be used, in particular related to thelevel of electrical energy as calculated from the ECG spectrum. In thecase of placing endovascular devices, one criterion may be that, at thelocation corresponding to the lower third of the SVC, the averageelectrical energy calculated from the endovascular ECG is twice as highas the average electrical energy calculated from the endovascular ECG atskin level or from a skin ECG in a corresponding lead, e.g., lead II.

Method for Placement of Central Venous Catheters

A method of placing a central venous catheter (CVC) is presented below.

-   -   1. Estimate or measure the required length of the vascular        access device (CVC) for the given patient.    -   2. If using saline and adaptor (200), go to step 11; if not,        proceed as follows. Insert a guidewire into the CVC and flush        align the guidewire tip and the catheter tip. Measure the length        of the guidewire outside the CVC. This measurement is necessary        in order to be able to realign the tip of the catheter and of        the guidewire after inserting the guidewire in the vasculature.        After taking the measurement, for example with sterile measuring        tape or with surgical thread, remove the guidewire from the CVC.    -   3. Gain vascular access and insert the guidewire for the        estimated required length.    -   4. Insert the CVC over the wire such as to leave outside the CVC        the length of the guidewire measured at step 1. Thus the CVC        inserted over the wire and the guidewire tip are flush aligned.    -   5. Connect a sterile electrical adaptor to the guidewire per the        instructions for use.    -   6. Connect the other end of the sterile electrical adapter to        the ECG cable of the electrography system.    -   7. Check that the display of the electrography system indicates        desired position of the catheter tip per the instructions for        use of the electrography system: in the lower third of the SVC,        at the caval atrial junction or in the right atrium. Typically,        the location of the tip of the catheter will be identifiable        through the specific shape of the P-wave and of the P-wave        relative to the R-wave of the electrogram and/or by the energy        levels and thresholds.    -   8. Adjust the position of the guidewire and CVC by pulling        and/or pushing them together as not to change the flush        alignment until the ECG waveform on the screen indicates that        the desired position has been reached. Correlate the actual        inserted length with the estimated length.    -   9. After the position has been reached, disconnect the        electrical adaptor and remove the guidewire.    -   10. Secure the CVC in location.    -   11. Continue here if saline and adaptor (200) are used.    -   12. Gain vascular access and introduce the CVC over the        guidewire as currently specified by the existing protocols.    -   13. Remove the guidewire    -   14. Attach the sterile adaptor (200) to the CVC.    -   15. Attach the electrical connection (234) of the adaptor (200)        to the ECG cable of the electrography system.    -   16. Fill a syringe with saline and connect it to the other end        of the adaptor (200). Flush the catheter lumen with saline as to        create a conductive saline column all way through the catheter        tip.    -   17. Check that the ECG waveform shown on the display of the        electrography system indicates desired position of the catheter        tip per the instructions for use of the electrography system: in        the lower third of the SVC, at the caval atrial junction or in        the right atrium. Typically, the location of the tip of the        catheter will be identifiable through the specific shape of the        P-wave and of the P-wave relative to the R-wave of the        electrogram and/or by energy levels and thresholds.    -   18. Adjust the position of the CVC by pulling and/or pushing        until the ECG waveform on the screen indicates that the desired        position has been reached. Correlate the actual length with the        estimated length.    -   19. After the desired position has been reached remove the        syringe and the adaptor (200).    -   20. Secure the catheter.        Method for Placement of Implantable Ports

A method of placing the catheter piece of an implantable port is similarto the method for placing a CVC. The adaptor (200) should be connectedto the catheter of the implantable port, and the syringe with salinemust be connected to the other end of the universal adaptor. A differentelectrical adaptor should be connected to a syringe needle placed in thecatheter of the implantable port. After reaching the desire position,the catheter should be connected to the implantable port.

Method for Placement of Peripherally Inserted Central Catheters Open andClosed Ended

Both open-ended and closed-ended peripherally inserted central catheters(PICC) can be placed as described herein, and the method of PICCplacement is similar to the one of placing CVCs. The inventive steeringmechanism described herein can be used to bend the tip of the PICC incase the catheter fails to advance in the desired direction

Method for Placement of Hemodialysis Catheters

A method for placing hemodialsys catheters is similar to the methodintroduced herein for placing CVCs. The inventive steering mechanismdescribed herein can be used to bend the tip of the hemodialysiscatheter in case the catheter fails to advance in the desired direction.Two different guidewires with adaptors (220) can be used for each of thelumens of the hemodialysis catheter as to guide placement of one lumeninto the right atrium and of the other lumen at the caval atrialjunction using the electrography system. Each of the lumens of thehemodialysis catheter can be placed independently in sequence or at thesame time by connecting the adaptors (220) of each of the lumens withdifferent electrodes of the ECG cable of the electrograph system.

Method for Placing Central Venous Access Devices in Patients withArrhythmias

Traditionally, patients with arrhythmias have been excluded fromprocedures of guiding central venous lines placement using theendovascular ECG method because of the lack of visible changes in theshape of the P-wave. The energy criteria for the P-wave analysisdescribed herein can be used to guide the placement of central venousaccess devices in patients with arrhythmias. In arrhythmia patients, theelectrical signals generated by the sino-atrial node have a certaindegree of randomness, such that they are not synchronized in order toproduce a consistent P-wave. Nevertheless, as previous studies haveshown, the electrical activity of the sino-atrial node exists andgenerates electrical energy of intensities typical to the proximity ofthe sino-atrial node. In one embodiment, the algorithm uses the energyas measured from the endovascular electrogram in order to map certainlocation in the vasculature. As such, this algorithm can be used toguide placement in patients with arrhythmias when only the electricalenergy is indicative of location but not the shape of the P-wave.

Method for Monitoring Tip Location and Certain Aspects of the ElectricalActivity of the Heart

Certain aspects of the electrical activity of the heart can be monitoredcontinuously or intermittently using the devices introduced herein.Either an electrical adaptor or adaptor (200) connected to theelectrography system can be used for monitoring. The electrical adaptorcan be connected to any stylet or other conductive member introduced inany venous access device or in any arterial device. Adapter (200) canalso be connected to any venous or arterial line as long as the infusionof a conductive solution, e.g., saline is possible. Adapter (200) canalso be used when electrically conductive fluids are inserted in thebody using an infusion pump. Monitoring the tip location and/or certainaspects of the electrical activity of the heart can be performed in anumber of clinical situations.

-   -   1. Adaptor (200) can be attached to a number of central venous        devices post insertion, e.g., at bedside and/or in home care        situations: PICCs, CVC, hemodialysis catheters. By connecting        the adapter to such a catheter and to an electrography system        according to the present invention and by injecting saline into        the catheter, the location of the tip of the catheter can be        confirmed and/or certain electrically activity of the heart can        be monitored during the time the adapter is connected by using        methods similar to those introduced above in the present        inventions.    -   2. Adaptor (200) can be connected to an arterial line between        the arterial line and the other devices connected to the        arterial line. The blood present in the arterial line and in the        universal adaptor ensures the electrical connection between the        blood and the electrography system. Thus the electrical activity        of the heart can be continuously monitored. This is particularly        important in the case of monitoring the preload changes which        translate in changes of the electrical energy of the heart        during the S-T segment of the ECG waveform.    -   3. Monitoring of the tip location and of the electrical activity        of the heart can also be achieved by using the electrography        system and connecting the adaptor (200) between a central venous        line and a pressure measuring system while performing central        venous pressure measurements.    -   4. In the case of an implanted port, a needle can be inserted        into the port chamber and the catheter can be flushed with        saline using a syringe filled with saline. An electrical adaptor        can be attached to the needle and to the electrography system.        The detected electrogram signal will contain information from        the skin level where the needle is in contact with the skin and        from the tip of the catheter through the injected saline column.        Since the impedance of the path to the catheter tip is lower        than the one to the skin, the detected signal contains both        components, i.e., at the skin level and at the tip of the        catheter. By subtracting the skin level signal, the signal at        the tip of the catheter can be estimated and thus the tip        position and certain electrical activity of the heart according        to the algorithms described in the present invention.

FIG. 13 illustrates the cardiac conduction system of the heart, whileFIG. 14 illustrates electrical signal propagation in the conductionsystem of the heart.

These figures illustrate the conductive mechanism of the heart, whichexplains why the electrical energy distribution within the heart asmeasured is indicative of specific locations within the heart.Accordingly, local electrical signals, behaviors and energyconcentrations can be measured and locations within the heart and bloodvessel can be determined more accurately; local heart conditions canalso be described more accurately.

The conduction system of the heart begins with the heart's dominantpacemaker, the sino-atrial node (1310). The intrinsic rate of the SAnode is 60 to 100 beats/minute. When an impulse leaves the SA node, ittravels through the atria along the Bachmann's bundle (1350) and theinter-nodal pathways, on its way to the atro-ventricular (AV) node(1320) and ventricles. After the impulse passes through the AV node, ittravels to the ventricles, first down to the bundle of His (1330) thenalong the bundle branches and finally down to the Purkinje fibers(1340). Pacemaker cells in the junctional tissue and Purkinje fibers onthe ventricles normally remain dormant because they receive impulsesfrom the SA node. They initiate an impulse only they do not receive onefrom the SA node. The intrinsic rate of the AV junction is 40 to 60beats/minute, the intrinsic rate of the ventricles 20 to 40beats/minute. The different propagation speeds of the electricalimpulses are shown in FIG. 14. From the SA node (1410) the impulsespropagate through the atrial muscle (1420) and through the ventricularmuscle (1460) at app. 0.5 ms, through the bundle branches (1440) and(1450) at app. 2 m/sec, through the Purkinje fibers (1470) at app 4 m/sand through the AV node (1430) at app. 0.05 m/s.

The electrical signals and the electrical energy distribution areadvantageously used to identify the proximity of the sino-atrial nodeand right atrial electrical activity even in the cases of arrhythmia,i.e., in the absence of a coherent P-wave measured by standard skinelectrocardiogram. While in some cases of arrhythmia random electricalsignal generated in the right atrium is not coherent enough to propagatethrough the body to the skin, the electrical energy is still present inthe right atrium and can be detected by local endovascular measurementsas a non-coherent P-wave, i.e., as significant electrical activity inthe P-segment of the ECG waveform. Energy measurements are also lesssensitive to some local abnormalities in impulse conduction: alteredautomaticity (arrhythmias), retrograde conduction of impulses, reentryabnormalities.

The electrical signals and the electrical energy distribution are alsoadvantageously used to quantify heart functionality, e.g., preload whichis related to the depolarization and extension of the heart muscle.

The electrical signals and the electrical energy distribution are alsoadvantageously used to guide guidewires and guiding catheters throughthe aorta into the left heart. This method is useful in simplifying theaccess to the left atrium and to the coronary arteries and in reducingthe amount of contrast and radiation needed to guide endovasculardevices to those locations. In a different application, the inventiveapparatus can also be used to guide catheters, e.g. Swan-Ganz throughthe right ventricle into the pulmonary artery. Other endovasculardevices can be guided and be used to measure endovascular electricalactivity in other locations of the cardiovascular system which areidentifiable by the cardiograms measured with the new apparatusintroduced in the present invention.

FIG. 15 illustrates electrical activity in the cardiovascular system dueto neuronal control system. Several paths of conduction are related tothe mechanism of control of heart (1530) and blood vessel (1520)activity: receptors (1510), e.g., pressure receptors transmitinformation related to the state of the blood vessels and to the stateof the heart to the nervous system through the Medullary centers (1500).The hypothalamus (1540) and the higher centers (1550) are involved inprocessing and reacting to the information received from thesensors/receptors. In turn they send impulses (1560) back to bloodvessels and the heart. By measuring electrical activity related to thecontrol system, information regarding heart conditions can be obtainedwhich could not have been obtained previously.

The many features and advantages of the invention are apparent from thedetailed specification, and, thus, it is intended by the appended claimsto cover all such features and advantages of the invention which fallwithin the true spirit and scope of the invention. Further, sincenumerous modifications and variations will readily occur to thoseskilled in the art, it is not desired to limit the invention to theexact construction and operation illustrated and described, and,accordingly, all suitable modifications and equivalents may be resortedto that fall within the scope of the invention.

What is claimed is:
 1. An adapter for an endovascular device,comprising: a body, including: a first open end designed to be connectedto a luer of a catheter, a second open end designed to be connected to afluid source, a central lumen, having a substantially cylindricalsurface, extending from the first open end to the second open end, thesubstantially cylindrical surface including a recessed portion, and achannel extending from the central lumen to an external opening; aconductive metal ring disposed in the recessed portion, the conductivemetal ring separated from the catheter by a section of the body when thefirst open end of the body is connected to the luer of the catheter; anda conductive wire, including: a distal end in contact with theconductive metal ring, and a proximal end extending through the channelat least to the external opening.
 2. The adapter according to claim 1,wherein the channel is sealed on at least one end.
 3. The adapteraccording to claim 2, wherein the external opening is sealed.
 4. Theadapter according to claim 2, wherein the conductive metal ring providesa seal for the channel.
 5. The adapter according to claim 1, furthercomprising a connector coupled to the proximal end of the conductivewire.
 6. The adapter according to claim 5, wherein the proximal end ofthe conductive wire extends to the external opening and the connector isattached to the body.
 7. The adapter according to claim 5, wherein theproximal end of the wire extends through the external opening and theconnector is spaced from the body.
 8. The adapter according to claim 1,wherein the first open end includes an elastic sealing portion.
 9. Theadapter according to claim 8, further comprising a removable cone pieceincluding a first end having an elastic sealing portion with a differentdiameter than the first open end of the adapter, and a second end toreceive the first open end of the body.
 10. The adapter according toclaim 1, wherein the second open end has a standard luer shape.
 11. Theadapter according to claim 1, wherein the surface of the central lumenis tapered along a longitudinal direction.
 12. The adapter according toclaim 11, wherein the surface of the central lumen is cone-shaped andthe first open end has a larger inner diameter than the second open end.13. The adapter according to claim 11, wherein the surface of thecentral lumen is cone-shaped and the second open end has a larger innerdiameter than the first open end.
 14. The adapter according to claim 1,wherein the channel extends from the central lumen between the firstopen end and the second open end.
 15. The adapter according to claim 1,wherein the channel extends at an angle from the central lumen.
 16. Theadapter according to claim 1, wherein the external opening is on anexternal surface of the body between the first open end and the secondopen end.
 17. The adapter according to claim 1, wherein the conductivemetal ring terminates prior to the first open end and the second openend.
 18. The adapter according to claim 1, wherein the first open endhas an internal diameter less than the central lumen and the second openend has an internal diameter greater than the central lumen.
 19. Theadapter according to claim 1, wherein the first open end has a firstdiameter and the second open end has a second diameter greater than thefirst diameter, the central lumen adjacent the first open end having areduced diameter portion with a third diameter less than the firstdiameter.
 20. The adapter according to claim 19, wherein the centrallumen linearly tapers from the first open end to the reduced diameterportion along an entire intervening length.
 21. The adapter according toclaim 19, wherein the central lumen reverse tapers from the reduceddiameter portion toward the second open end to a constant diameterportion with a fourth diameter greater than the first diameter and lessthan the second diameter for a length greater than the length of theconductive metal ring, wherein the conductive metal ring is disposed inthe constant diameter portion.